A typical couple gets £209.70 per week with a basic state pension and pension credit, but but if one partner is below the age of 60, they will get just £105.95 per week from 2013.

Age UK said this group of people could also lose the right to other linked benefits, such as cold weather payments.

People with savings of more than £16,000 will also lose the right to claim pension credit, while those with savings of more than £6,000 will see a steep withdrawal of support.

Michelle Mitchell, Charity Director of Age UK, said: “Many of those nearing the State Pension Age can find it difficult to find work no matter how hard they try.

"Just because one half of a couple is below pension credit age does not mean that their income needs drop and for those suffering unable to work through sickness or caring for others there is no opportunity to supplement their partner’s income.”

The charity is also worried that the changes are quietly being introduced as part of the Government’s Welfare Reform Bill.

“We are extremely concerned that there has been no consultation on such a major policy change and full details of the system are not yet available even though the Welfare Reform Bill has been considered by the House of Commons and is entering its last stages in the House of

Lords,” Ms Mitchell added. “There are just too many questions that have been left unanswered.”

The Government is also in the process of changing the state pension age. It will rise for women from 60 to 65 and everyone will then see this age raised to 66 by 2020.

In his Autumn Statement last month, George Osborne announced that the state pension age will further rise to 67 between 2026 and 2028 – a decade earlier than previously planned. This will mean those aged 44 to 51 will be forced to work for an extra year.

A spokesperson from the Department for Work and Pensions said: “We’re clear that people of working age who can work, should be expected to do so, and it’s not right that the existing system allows a younger partner to receive benefits meant for pensioners.

"Claiming universal credit strikes the right balance between providing the necessary financial help while ensuring that those who can work, are incentivised to do so. This change will not affect couples currently claiming pension credit.”